There is known a cellular phone including: a display casing having a display screen; operation casing having operation keys; and connecting means adapted to connect the both casings to each other, wherein the display casing is rotatably held in a plane parallel to the display screen relative to the operation casing.
In such a cellular phone, switching between a vertically long state in which a longer direction of the display screen is made vertical and a horizontally long state in which the longer direction is made horizontal by rotating the display casing can be performed to use the phone.    Patent Document 1: Japanese Unexamined Patent Publication No. 1991-250360    Patent Document 2: Japanese Unexamined Patent Publication No. 1998-26964    Patent Document 3: Japanese Unexamined Patent Publication No. 1998-49334    Patent Document 4: Japanese Unexamined Patent Publication No. 2005-241652